6.3 The extraction of aluminium

Question 1

What are the uses of alluminium

Answer 1

• pans
• cooking foil
• drink cans

Question 2

Where can you get aluminium oxide from

Answer 2

ore called bauxite

Question 3

Explain why aluminium cannot be extracted from its oxide by reduction with carbon

Answer 3

Carbon is not reactive enough to use in its extraction so cannot displace aluminium

Question 4

Explain why cryolite is added

Answer 4

Reduces overall melting point and energy needed

Question 5

Explain why the carbon electrodes must be replaced frequently

Answer 5

oxygen reacts with hot carbon anodes making carbon dioxide, so carbon anodes gradually burn away, needing to be replaced regularly

Question 6

Give two reasons why the extraction of aluminium is expensive

Answer 6

High melting point requires a lot of energy, replacing positive electrodes

Question 7

Write half equations for the reactions at the anode and cathode, and if they are oxidiation or reduction, for the extraction of aluminium

Answer 7

Anode: 2O²- -> 0₂ + 4e-
Oxidation

Cathode
A³+ + 3e- -> Al
Reduction

Question 8

Name the compound from which aluminium is extracted

Answer 8

bauxite